4 lug Ghia wheels vs. bug wheels

I am trying to find out how 4 lug Ghia wheels and 4 lug Bug wheels differ, if they do. I have asked VW people that have more knowledge than I do and half say no difference and half say Ghias have a deeper offset.
On The Samba I found several references to Ghias having greater offset, but they don't agree on hat the offset is. The best I can find so far is: Ghia - 4.5J X 15 ET41 (some say ET46), Bug - 4J X 15 ET40.

Can anyone shed anymore light on this for me? It is time to put the 70 Ghia back together and I'd like to use proper wheels. Thanks.

Did you see this? But looking at the original owners manual for 1970, the ghia says 4.5jX15, and the beetle manual says 4jX15.

I did not look there.   That is why I posted my question here where those more resourceful than I hang-out.  
Thanks.